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TA infrasound detections are produced by regularly scanning the USArray Transportable Array broadband infrasound data (40 Hz BDF channel) and generating weekly detection lists. These lists contain raw detections (full and cutomized) without event association or categorization and highlight time intervals that may contain signals of interest (…more information ). A relatively low detection threshold is chosen and relative amplitudes are given in order allow greater flexibility to users. This results in long detection lists.

The detectors utilized by this product are:

power spectra detector — calculates power spectra of the signal as a function of time in pre-defined frequency bands. A characteristic function based on the signal’s mean power in the band of interest is used for detection. Some infrasound signals are emergent with long durations. For these signals, their characteristics are often sharper and more easily detected in the frequency domain than in the time domain STA/LTA approach below.

STA/LTA-based detector — a detector similar to the classic STA/LTA detectors with an additional fixed time gap between STA and LTA windows to compensate for the emergent nature of the infrasound signals. This gap reduces the level of LTA contamination by the signal.

Table below contains links to the available weekly detection files. For a list of parameters used by the infrasound detectors see the TA Infrasound Detections product page . Two detection lists, full and customized, are compiled for each detector. The longer full lists provide all detections while the shorter, more conservative, customized lists use additional metrics .

Notes:

Station coordinates for each week could be downloaded as a text file via the station list links below.

Daily customized power spectra detection KML files are available via the KML file links below. To view TAID detection animations you need to adjust the Google Earth time slider (click here for more information).

Week numbers follow the ISO system in which the week-numbering year starts at the first day (Monday) of week 01 and ends at the Sunday before the new ISO year. if January starts on a Monday, Tuesday, Wednesday or Thursday, it is in week 01. If January starts on a Friday, Saturday or Sunday, it is in week 52 or 53 of the previous year.

The weekly detection files with ‘*’ next to their week number have been updated in the past 24 hours.